Maintaining the sterility of drinking water supplies is a major factor in reducing the health risks to human populations. While large metropolitan water systems can make use of highly toxic chlorine gas for sterilizing drinking water, such systems are impractical in remote locations, which lack highly trained personnel and the equipment to maintain the systems. There are many settings in which sophisticated systems are not practical. For example, campers or military personnel in the field cannot be expected to operate such a system to provide potable drinking water from streams or other potentially contaminated water sources. To be effective in such rural settings, a system must be capable of running for long periods of time with little or no maintenance. In addition, the raw materials required by the system must be readily available.
Systems based on the electrolytic production of chlorine and/or other chloro-oxygen species based germicidal agents are particularly attractive for use in the present invention. These systems require only electricity and common salt as raw materials. One such system is described in U.S. Pat. No. 4,761,208 to Gram, et al. entitled Electrolvtic Method and Cell for Sterilizing Water, which is incorporated herein by reference. The system of the present invention utilizes an electrolytic cell to generate an oxidant solution including chlorine in the form of hypochlorous acid and other chloro-oxygen species. Other embodiments of the present invention produce an oxidant solution that is predominantly sodium hypochlorite. The oxidant solution is produced from a brine solution using common salt. This oxidant solution may be added directly to the drinking water at a dilution ratio compatible with the concentration of the oxidant produced in the device and the demand of the water. The oxidant produced is more effective at inactivation of micro-organisms than is conventional chlorination technology, including chlorine gas, sodium hypochlorite, and calcium hypochlorite. At adequate dilution ratios, the water is sterilized without causing the water to become unpalatable. This technology is particularly attractive because of its simplicity and long maintenance free operation time. Studies have been conducted to demonstrate the micro-organism inactivation effectiveness of the oxidant, commonly referred to as mixed-oxidant solution. Linda V. Venczel, Michael Arrowood, Margaret Hurd, and Mark D. Sobsey with the University of North Carolina at Chapel Hill, N.C. have conducted research and published a paper entitled, Inactivation of Cryptospordium parvum Oocysts and Clostridium Perfringens Spores by a Mixed-Oxidant Disinfectant and by Free Chlorine, published in Applied and Environmental Microbiology, Apr. 1997, p. 1598-1601.
The systems based on mixed-oxidant production have been used successfully in rural communities with small water supplies to larger municipal water systems treating millions of gallons per day. These larger systems are not well suited for use by individual campers and personnel in the field who must treat small quantities of water on a daily basis. The mixed oxidant systems designed to date are applicable to large quantities of water and are large and heavy. In addition, these systems require quantities of electrical power that are not practical at the mesoscale, or individual person level.